Compressor unloader



Dec. 23, 1958 G. w. HARTWELL COMPRESSOR UNLOADER 2 Sheets-Sheet 1 Filed May 27, 1955 ll l H6. 5 GEORGE W. HARTWELL INVENTOR. MAM

Dec. 23, 1958 G. w. HARTWELL COMPRESSOR UNLOADER 2 Sheets-Sheet 2 Filed May 27, 1955 L L B. '5 5 M 0 /A// w. Wm AE I I 4 W 6 7 .I 3 3 1 W I "a M H/ 3 G I I R 2 ll W m o w G 9 B B M 5 3 l lll Ill 5 o 4 I 7 w u O 1U 2 I 4 46 m n 5 n/ n 3 M B H I l Ill 5 .4. m 4 a 4. 7. w 24 \1 9 I. ll 9 B 3 s 2 a 4 8| 2 W 0 m 2 2 a w a. 44 w I I II 5 ll. 6 3 M N Z Z 7 9 3 8 5 2 v M. 5

T designates a multi-cylinder disposed in cylinders 12 i plates 14 and 15 are inder head 13 in alignment With the upper 'inder 12. Spaced rectangular slots '16 are disposed-in 2,865,557 conusson UNLOADER George W. Hartwell, South Hadley, Mass, assignor to Worthington Corporation, Harrison, N. J., a corporation of Delaware Application May 27, 1955, Serial No. 511,561 vClairns. (Cl. 230-31) The present invention relates to a fluid compressor and lmore particularly to means for varying the output or capacity of said compressor.

In fluid compressors designed to operate at relatively I constant speed, the load on the system in which the compressor is arranged 'inefiicient operation of the compressor unless the capacity of the compressor can be varied to comply with the sys may sometimes vary resulting in an tern variations;

In accordance with the present invention, a compressor is provided having novel unloading means thereon to vary the output or capacity of the compressor to meet the varying capacity which may be required in the system in which it is arranged, which results in a considerable savingin operating power. v

I In accordance with the present invention, a fluid cornpressor is provided Wllhl'lOVBl unloading means disposed in the cylinder head of the compressor cylinder whereby gas from the high pressure side of the compressor actuates the unloading means to place the cylinder inlet valve means in a loaded position to control the capacity of the compressor.

The novel unloading means of the present invention further engages the cylinder inlet valve means in a uniformly steady action to prevent damage to said valve means when unloading occurs.

The invention will be better understood from the following description when considered in connection with the accompanying drawings forming a part thereof'and to the drawings, the reference numeral compressor having pistons 11 for reciprocating movement therein. A cylinder head 13 is disposed adjacent the upper end of a cylinder 12.

Referringto Figures 3 and 4, upper and lower valve disposed in the lower portion of cylend of acylupper plate 14: in alignment with a rectangular shaped opening. 17 in the lower plate 15.

' f' ,A suction valve 18 is positioned in opening 17comprising a rectangular plate '19 having spaced rectangular-slots Sttes Patent 0 "ice 20 therein. Plate 19 is disposed in opening 17 with slots '20 spaced alternately of slots 16in upper plate 14. The

portion of plate 19 between slots 20 is provided with con- .cave recesses 21 (Fig. 3) in the upper portion thereof. Flat strips 22 made of a flexible or resilient metallic ma-- terial are positioned in alignment with slots 16 and are re strained at the'opposite ends thereof between plates 14 and 19(see Fig. 3). Strips 22 are adapted to seat against plate 14 to close off or seal slots 16 andto be bent down-- wardly into contact with the surface forming concave recesses 21 to open the suction valve on the suction stroke of the piston, as hereinafter described.

A discharge valve 23 is positioned adjacent suction valve-18 in a'rectangular opening 24 in upper plate 14 in alignment with a plurality of spaced rectangular slots 25 disposed in lower plate 15. Valve 23 comprises a rectangular plate 26 having spaced rectangular slots 27 therein. Plate 26 is positioned in opening 24 with slots 27 disposed alternately of slots 25 in the lower plate 15. The portions of plate 26 between slots 27 are provided with concave recesses '28 (Fig. 3) in the lower portion thereof. Flexible metallic strips 29 are provided in alignme'nt with slots 25 and recesses 23 and are restrained at 'the opposite'ends'thereof between plates 15 'and 26 (see Fig.3). Strips 29 are adapted to seal off slots 25 and to be bent upwardly into contact with the surface forming concave-recesses 28't'o open the discharge valve on the compression stroke of the piston-11, as'hereinafter described. Suction valve 18 communicates with a cylinder inlet chamber 30 while discharge valve 23 communicates with a discharge chamber 31 disposed in cylinder head 13.

An unloading device '33 is disposed in cylinderhead' 13 in alignment with suction valve 18 and comprises a piston 34 having'a piston rod35 positioned in a cylinder 36. Piston 34 is maintained in its lowermost position in cylinder 36 by a spring or biasing means 37 (Fig. 4) disposed ina cap member 38 threaded into the upper portion of the cylinder head.

The'lower end of piston rod 35 extends through a bore 39 "disposed in cylinder head'portion 40 into the lower portion of the suction chamber 30. Bore 39 is of s'ufficient size to provide a small clearance between the piston rod and'inner surface thereof to permit communication of cylinder 36 with the suction chamber through said bore. A horizontally extending bar 41 having plungers or fingers 42 extending therefromis fixed to the lower end of piston rod 35. Fingers 42 extend into slots 16 into contactwith the metal strips 22 therein and bend or flex the strips into engagement with recesses 21 to maintain the suction valve in an opened position, as hereinafter described. One

finger is provided with an extension 4251 on the upper end thereof adaptedto fit loosely within a bore 441a (Fig. 4) drilledin head portion 40 to keep bar 41 from turning or rotating and'the fingers from getting'out of alignment with slots 16.

' Control means in the form of a'solenoid valve'43 is provided in the cylinder head in alignment with discharge valve 23" having a plunger 44- which extends into aportion of a passage'45 disposed in cylinder head portion 40 in communication with the lower portion of cylinder 36. A

spring 43' 'is provided for the solenoid valve to maintain the plunger in a lowermost position seated against nozzle 6 member 4-6 disposed in thepassage to close 01f the orifice 46a'therein. An air strainer 47 is disposed in the passage adjacent the inlet portion of member as. Discharge chamber 31 is'in communication with passage 45 through 'an orifice 48 boredthrough portion 40, and with the dis- 1 charge manifold of the'compressor (not shown).

Patented Dec. 23, 1958;

In operation, when the compressor is driven by a constant speed prime mover (not shown) the compressor pistons 11 will be reciprocated in cylinders 12. The movement of a piston 11 downwardly in the cylinder 12 will create a vacuum in the cylinder so that fluid in suction inlet chamber 30 will force suction valve strips 22 downwardly into engagement with the bottom of concave recesses 21 to permit the fluid to flow into inlet slots 16 and through recesses 21 and outlet slots 20 into the upper portion of the cylinder. When piston 11 moves upwardly in the cylinder, the fluid therein is compressed and forces strips 22 upwardly in contact with the edges of plate 14 adjacent slots 16 to close the suction valve, and forces strips 29 of discharge valve 23 upwardly in contact with the surface forming recesses 28 to. open the discharge valve and discharge the fluid into chamber 31.

When it is desired to load a compressor cylinder provided with the unloading means of the present invention, solenoid valve 43 is energized by means not shown and lifts plunger 44 upwardly against the tension in spring 43' and out of contact with nozzle member 46 to. open the orifice therein. Thereafter, high pressure fluid supplied from the compressor discharge manifold, not shown, passes into chamber 31 and through orifice 48 and strainer 47, passage 45, nozzle 46, and into the portion of passage 45 adjacent cylinder 36. Thereafter, the fluid impinges against the bottom of piston 34 and moves the piston upwardly in the cylinder against the tension in spring 37. Piston rod 35 moves upwardly with, the piston thereby lifting fingers 42 out of contact with strips 22. There after, resilient strips 22 flex back to their original flat shape and seat against plate 14 to close olf or seal inlet slots 16. Thus valve 18 is then positioned to open and close in response to the movement of piston 11 in the cylinder as described above.

During the loaded operating period of the compressor, a portion of the high pressure gas in passageway 45 and bottom of cylinder 36, will flow through bore 39, around piston rod 35, to the suction chamber. This flow is so small an amount because of the small space between bore 39 and piston rod 35, that the high pressure under piston 34 is maintained at a high level so as to hold up piston 34 against the force of spring 37. This flow is also not sufiicient to noticeably affect the gas pumping ability of the compressor.

When it is desired to unload the compressor cylinders provided with the unloading means of the present invention, solenoid valve 43 is deenergized and spring 43' lowers plunger 44 in the passage until it seats against nozzle 46 and closes oil? the supply of high pressure fluid from chamber 31 to the lower portion of cylinder 36. Thereafter, high pressure fluid in cylinder 36 and passageway 45 leaks or bleeds through bore 39 around piston rod 35 to suction chamber 30, and spring 37 gradually lowers piston 34 to its lowermost position in the cylinder until bar 41 forces fingers 42 into contact with strips 22 and bends or flexes the strips downwardly into contact with the bottom of concave recesses 21 to maintain the suction valve in an opened or unloaded position. Thus, the present invention provides an unloading device having means for gradually bleeding off high pressure fluid from the unloader cylinder to cushion the blow of the unloading fingers on the suction valve when unloading the valve. Thereafter, when piston 11 is reciprocated in cylinder 12 there is no pumping or compressing of fluid, since fluid passed into the cylinder on the intake stroke returns to the suction inlet chamber on the compression stroke.

It will be noted that the present invention provides a finger having an extension 42a which extends into a bore 40:: in cylinder portion 40 in a loose fitting manner to keep bar 41 from turning so that fingers 42 will not get out of line with the valve slots 16 and thus prevents any breakdown in operation of the unloading means.

It will be understood that the invention is not to be limited to the specific construction or arrangement of parts shown but that they may be widely modified within the invention defined by the claims.

What is claimed is:

1. In combination with a compressor having a cylinder including a movable piston therein, a suction valve and a discharge valve for the compressor, a cylinder head for the compressor cylinder and including inlet and outlet chambers communicating respectively with the suction valve and the discharge. valve, of unloading means in said cylinder head comprising an unloader cylinder formed in spaced relation with the suction valve, a bore through the unloader cylinder and in communication with the inlet chamber, piston means in the unloader cylinder, a rod of lesser diameter than the bore extending therethrough and connected at one end to the piston of the unloading means, finger means in the inlet chamber and connected to the other end of the rod and adapted to extend into the suction valve, biasing means engaging the piston of the unloading means to move the finger means into contact with the suction valve to open the suction valve, a plurality of bores within the cylinder head providing passage means for the fluid being compressed and from the outlet chamber to the piston of the unloading means, a nozzle in the passage means formed by said plurality of bores, control means for said nozzle and selectively seated thereon for regulating the flow of high pressure fluid from the outlet chamber to the piston of the unloading means, and a restricted passageway formed by the outer periphery of the rod and the bore whereby when the control means is operative to close ofi communication from the outlet chamber to the piston of the unloading means fluid leaks through the re stricted passageway to the suction chamber to permit a gradual lowering of the piston of the unloading means to force the finger means into contact with the suction valve.

2. The combination claimed in claim 1 wherein the finger means includes an extension thereon and the extension is loosely mounted in the cylinder head so that rotation and misalignment of the finger means are prevented.

3. Thecombination claimed in claim 1 wherein the control means comprises a solenoid having a plunger adapted to be selectively seated on the nozzle disposed in the passage means to control the passage of high pressure fluid therethrough.

4. In combination with a compressor having a cylinder including a movable piston therein, a suction valve and a discharge valve for the compressor, a cylinder head for the compressor cylinder and including inlet and outlet chambers communicating respectively with the suction valve and the discharge valve, of unloading means in said cylinder head comprising an unloader cylinder formed in spaced relation with the suction valve, a bore through the unloader cylinder and in communication with the inlet chamber, piston means in the unloader cylinder, a rod of lesser diameter than the bore extending therethrough and connected at one end to the piston of the unloading means, finger means in the inlet chamber and connected to the other end of the rod and adapted to extend into the suction valve, biasing means engaging the piston of the unloading means to move the finger means into contact with the suction valve to open the suction valve, a plurality of holes within the cylinder head providing passage means for the fluid being compressed and from the outlet chamber to the piston of the unloading means, a nozzle in the passage means formed by said plurality of bores, solenoid means having a plunger extending into the passage means and adapted to be selectively seated on the nozzle for regulating the flow of high pressure fluid from the outlet chamber to the piston of the unloading means, and a restricted passageway formed by the outer periphery of the rod andjthe bore whereby when the control means is operative to close otf communication from the outlet 5 chamber to the piston of the unloading means fluid leaks through the restricted passageway to the suction chamber to permit a gradual lowering of the piston of the unloading means to force the finger means into contact with the suction valve.

5. The combination claimed in claim 4 wherein the finger means includes an extension thereon and the extension is loosely mounted in the cylinder head so that rotation and misalignment of the finger means are prevented.

References Cited in the file of this patent UNITED STATES PATENTS Hibbard Aug. 23, Sparacino Oct. 24, Bartholomew Nov. 1, Nordberg Nov. 1, Nordberg Nov. 1, Biehm June 19, 

